[Cryptography] Terakey, An Encryption Method Whose Security Can Be Analyzed from First Principles

[Peter Fairbrother]

On 23/07/2020 03:12, Arnold Reinhold via cryptography wrote:

> The analysis of Terakey (https://www.researchgate.net/publication/342697247) consists of a series of levels. For the basic level, the attacker is assumed to know the PRNG algorithm and the message indicators, ciphertext and plaintext of all past traffic. Under these assumptions, the attacker would therefore know the locations and contents of all the Terakey bytes used for past traffic. The only thing relied on from the PRNG is providing a reasonable approximation of a uniform random sampling of the Terakey. It is well established that PRNGs can do that.
> 
> The security analysis then consists of estimating the likelihood of a cypherbyte already known to the attacker 

Oh no no no. That might be your analysis, but it isn't the only analysis.

Suppose I am the NSA and manage to tweak the PRNG to my nefarious means.

Perhaps I can arrange that 1 in 3 selections is to a limited set of 
terabyte bytes. After getting some known plain/cyphertext traffic I can 
read 1/3 of the plaintext characters - enough to do serious damage.

Peter Fairbrother